Electric glow discharge lamp



Aug. 16, 1949. `ca. E. INMAN ELECTRIC GLOW DISCHARGE LAMP Filed Feb. 5, 1947 u M m w m n,

w un. rnungnu Irwnve-rw'or-i Geer- 9 E. Infjngn, O LJ @l I His ATTor-ngeg Patented Aug. 16, 1949 to General Electric Company,'a

New York corporation of Application February s. 1941, semi No. 726,603

2 claims. (Cl. 17e- 122) 1 My invention relates to gaseous electric discharge devices generally, and more particularly to electric discharge lamps of the cathodic glo type.

An object of my invention is the provision of a full-waverectifying lamp of the cathodic glow type having a cathode and two anodes so constructed and arranged that the anodes surround the cathode but do not obstruct appreciably the radiation of the glow discharge which comes from the space surrounding the cathode. Another object; is to produce a lamp having the advantage of greater freedom from blackening than is the case with other constructions heretoforey used. Another advantage of lamps constructed in 'accordance with my invention is the virtual elimination of radio interference. Still another advantage is that long life can be obtained in a short bulb type lamp without; changing the arc characteristics, because the hot spot can travel along the relatively long cathode, as the emissive coating is used up, without changing the spacing between the cathode and the anodes.

In the drawing, Fig. 1 is an elevation of a singleended lamp comprising my invention, together with a diagram of a suitable circuit therefor, and Fig. 2 is a similar view of a double-ended lamp and circuit.

Referring to Fig. 1, the lamp comprises a glass bulb I containing a suitable ionizable medium such as a gas like argon or neon, or a vaporizable metal like mercury, or mixtures thereof. The bulb I also contains a thermionic cathode 2 which is preferably arranged axially on a pair of surrounding coiled wire anodes 3, 4 arranged in the form of a double helix. The said cathode 2 may consist of a coiled or coiled-coil lament of tungsten with a loose overwind of finer tungsten wire, and activated with a suitable electron emissive coating, such as alkaline earth oxides. The cathode 2 is mounted on the ends of lead-in wires 5, 6 and the anodes 3, 4 are mpunted on leads 1,.

l, the said leads 5, 6, 1, 8 being sealed through a stem 9 at the end of the bulb I and being arranged in the four corners of a square at the upper end of said stem.

The anodes 3, 4 are made up of spirals of wire such as nickel or aluminum. The two spirals are fitted together so that they exhibit a cylindrical form but do not touch each other. A slmple way of making such a double helix of definite well-defined shape is to hold a piece of straight wire at its center portion and wind spirals simultaneously from the two ends in a jig or Winder. The connecting piece of wire can then be cut out 2 after the two ends have been mounted on the lamp stem 9. For the sake of rigidity it is desirable to have the two spirals connected by an insulating member such as a bead of glass Il. This might be done rst if desired. For example, if one starts with two pieces of molybdenum wire for making the spirals, one end of eachcould be inserted into a glassbead or button and this button would then be the starting point for winding the two spirals on the jig. t

The size of the anode wire and the number of turns and the diameter of the spirals all depend upon the current used and the gas or vapor pressure which is desirable. In the case of an ionizable atmosphere of mercury with 4 mm. of argon gas and a current of .3 ampere, spirals made of two turns of 20 mil wire with a diameter of l/2 inch are suitable. This means that there isa total of four turns in the double anode, and the length of the anode is in the neighborhood of l/2 to 1%, inch. 'I'he bulb size in this particular case would be about 1 inch in diameter.- In order to prevent flash-over between the two anode spirals, it is preferable that the distance between the two anode wires be not appreciably less than the distance between either one of the wires and the cathode. Suitable dimensions are a spacing of l approximately 1/4 inch between the anodes, and

a diameter of S inch for the anode spiral, which leaves V4 inch spacing between the cathode andl anode.

'The construction described above provides a small alternating current, single-ended lamp which permits easy starting and allows the radiation from the glow surrounding the cathode to be readily emitted beyond the anodes. Two special adaptations of this lamp are as a fluorescent lamp or a germicidal lamp. In the case of the fluorescent lamp, the interior surface of the bulb I may be coated with a suitable phosphor which is excited by the short wave ultraviolet radiations emitted by a lamp containing mercury vapor. In the case of a germicidal lamp the bulb I is made of a special glass which transmits those ultraviolet radiations. V

A lamp of the type described herein has much greater freedom from blackening than other constructions heretofore used. Also, the amount of radiation from the lamp is approximately uniform in all directions, thereby causing no obstruction in any one or two directions as would be the case if two anode plates were used. The spirals also provide a large anode area which is desirable. Furthermore, the uniform anode placement insures that the same hot spot is efiective through both half cycles; consequently with no shift of the hot spot, radio interference is practically eliminated. This etlect is further insured by the fact that the two spiral anodes form a sort of screen around the cathode which tends to minimize any slight amount of interference which might remain.

As shown in Fig. 1 the anodes 3, I are connected. through their leads 1, 8, to the terminals II, I2 oi' a suitable source of current supply. The cathode 2 is connected, through its leads 5, B, to respective ends of a pair of choke coils I3, I4 which have their opposite ends connected to the terminals II, I2. Thus, there is a continuous ilow of current through the cathode ,2 which may have a potential drop of about 10 volts. The current supply source I I, I2 may have a potential of 60 volts, while the lamp operates at a current of about 300 milliamperes at a voltage of about 15 volts. The choke coils I3. I4 serve alternately as stabalizing impedance for the discharge between cathode 2 and anodes 4 and 3 respectively.

The lamp shown in Fig. 2 is essentially the same as that shown in Fig. 1 except that it is of the double-ended type having a stem 9 at each end thereof. Corresponding parts of the lamp shown in Fig. 2 have been numbered the same as their counterparts in Fig. 1 with the addition of a prime to the numeral. The auxiliary apparatus shown in Fig. 2 includes a transformer the primary I5 of which is connected to the terminals IB. I'I of a source of supply which may be a commercial 11S-volt 60-cycle line. The anode leads 1 and 8' are connected to suitable taps on the primary I5. The cathode leads 5' and 6' are connected to the ends of the secondary I8 which has a connection I9 between its mid-point and the mid-point of the primary I5.

WhatIclaimasnew and desiretosecureby Letters Patent of the United States is:

1. A gaseous electric discharge lamp of fullwave rectifying type comprising a sealed envelope containing an ionizable medium, a thermionic activated cathode in said envelope, and a pair of coiled wire anodes surrounding said cathode and arranged in the form of a double helix, the distance between said anodes being not appreciably less than the distance between either of said anodes and said cathode, said anodes being exposed directly to said cathode along straight lines therebetween.

2. A gaseous electric discharge lamp of fullwave rectifying type comprising a sealed envelope i REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Holst et a1 July 3, 1928 Ewest Dec. 18, 1934 Number 

